This proposal is an application for a new 5-year National Research Service Award Institutional Research Grant to support a training program in HIV Epidemiology and Prevention Sciences at the Johns Hopkins Bloomberg School of Public Health (BSPH) and the Johns Hopkins School of Medicine (SOM), entitled the Johns Hopkins HIV Epidemiology and Prevention Sciences Training Program. The proposed program would be led by Director Chris Beyrer MD, MPH, and Deputy Director Shruti Mehta PhD, MPH. We are requesting support for 4 pre- and 2 post-doctoral trainees. The program mission is to train pre-doctoral students and post- doctoral fellows to become leaders at the forefront of research in HIV/AIDS with advanced competencies and state-of-the-art skills in three training tracks: HIV Epidemiology Research Methods and Translational Sciences which includes training in (1) Populations and Study Designs, including identifying, recruiting, and retaining populations relevant for HIV research and global HIV epidemiological cohort studies; (2) Measurement issues in HIV populations, including innovative methods for surveillance, estimation of HIV prevalence and incidence, and novel population-based measures of disease burden; (3) Inference techniques, including modern analytical methods for causal inference and mathematical modeling; and (4) Synthesis and Translation of research findings to public health practice, including systematic reviews/meta-analyses and implementation science. HIV Clinical Epidemiology and Laboratory Sciences including training in (1) the epidemiology of major co-infections and co-morbidities associated with HIV, (2) Measurement of the spectrum of genetic, virologic, immunologic, and clinical factors. HIV Prevention Sciences including how to prevent and reduce the burden of HIV through training in (1) Behavioral Science aspects of HIV acquisition and transmission, (2) Design and Analysis of HIV biomedical and behavioral prevention trials, including treatment as prevention research (TasP), and (3) Community-based and Population-level approaches to HIV prevention and control beyond individual behavior change. The program goal is to create a rich and interactive trainee environment augmented by the exceptionally innovative, productive, and collaborative HIV research conducted by observational, clinical, and prevention scientists throughout Johns Hopkins BSPH and SOM.